balancing wheels/tyres is not as easy as it looks, most people especially at the like of the 'roadside tyre companies' dont know how to get it right with the minimal weights.
counter balancing is a problem ive seen so many times when a car has been to the likes of kwik fit for instance. which is putting one weight on the wheel ( inside for instance) because the balancing machine tells them to , then re-spinning the wheel and it will tell them to stick another weight, same side, but in a differant position or opposite the original weight.

can be attributed to what your experiancing, or just generally shit wheels or, as there more commonly know rondells